Which of the following is NOT a property of complementary angles?

Complementary angles are defined as two angles whose measures add up to 90 degrees. This fundamental property is crucial to understanding the nature of these angles.

Given this definition, let's delve into the other choices to clarify which property is not characteristic of complementary angles. Complementary angles can indeed be adjacent, meaning they share a common ray or side, or they can be non-adjacent, which means they do not share a side but still satisfy the condition of summing to 90 degrees. Both of these scenarios hold true in geometry.

The property that states they form a straight line, however, is inaccurate for complementary angles. A straight line measures 180 degrees, which clearly exceeds the requirement for angles to be complementary. Thus, identifying this property as not relating to complementary angles is correct, reinforcing the understanding of their definition and characteristics within geometry.